Fix headerTest

Summary: It was written to the old api

Reviewed By: @alexmalyshev

Differential Revision: D1698880

Signature: t1:1698880:1416617532:3111a9d67b0624be5cbfccbea7bf019a192028e2
typechecker: add constants to hh_client --show

Summary: ... it's valuable for checking whether a builtin constant is declared.

Reviewed By: @jwatzman

Differential Revision: D1696607

Signature: t1:1696607:1416616316:bb07a63e2dd07da4ac39014ea8fbc0252ecba5b0